Over the years, the title of Avengers has been associated with heroism. They are the Earth's mightiest heroes. However, everyone deserves a second chance, and Marvel's villains are no exception. One would hardly expect villains to join Marvel's most notable superhero team, some of them have had a change of heart over the years and switched sides. Here are five Avengers who were villains. The Avengers movie already hinted at Black Widow's dark past. However, not many fans might know that Natasha was not only a villainous spy but also responsible for corrupting and leading Hawkeye down a path of villainy. She also tried to destroy Iron Man. However, she changed sides during 'Avengers #32' and fought the Sons of the Serpent, eventually becoming an iconic Avenger. Sandman is one of the best examples of a villain trying to save his soul. Originally a Spider-Man villain, Sandman was urged by The Thing, of Fantastic Four, to reconsider life choices. This led him to join the Outlaws, a group of reformed criminals aiding Spider-Man. In 'Avengers #329', Captain America granted him a 'Presidential' pardon and dubbed him an Avenger. Rogue is one of the most notable members of the X-Men. However, she started her career as a villain. Initially, a member of the Brotherhood of Evil Mutants, Rogue was hired by Mystique. However, after absorbing the powers of Captain Marvel, Rogue underwent a change of heart and joined the X-Men. She would later go join the Avengers Unity Division. Venom has been a symbiote in the Marvel Universe who has bonded with various hosts like Eddie Brock and Mac Gargan. Over these periods, Venom was established as a villain. However, when Flash Thompson, a soldier, was given the symbiote, he put a fresh spin on the character. Agent Venom became a hero as Flash joined the Guardians of the Galaxy and Secret Avengers. Scarlet Witch or Wanda Maximoff is one of the most powerful mutants in the Marvel Universe. She is Magneto's daughter. Although she is one of the strongest Avengers and on the side of heroes now, this was not always the case. She started as a member of Brotherhood of Evil Mutants before leaving on her own and joining Captain America's side.